Touch screens have had enormous growth in many areas of modern life. Touch screens are now common in places such as kiosks at airports, automatic teller machines (ATMs), vending machines, computers of all kinds. The elimination of the need for a pointing device and/or a light pen in many applications has been widely successful.
There are several different touch technologies, many of which differ in the way that touch is detected. For example, capacitive technologies that utilize the finger as a shunt for a small alternating current that is run to ground through the operator's body. With scanning infrared systems, a user's touch is registered when a finger (or a stylus) encounters an array of infrared beams. There is also a surface acoustic-wave touch screen, wherein the screen absorbs the acoustic waves propagating on the touch surface, and the touch is identified by the drop in acoustic signal from the touch location. Resistive touch technologies are based on two layers of conductive material held apart by small, barely visible spacers. When the screen is touched, the two layers come into contact, and two-dimensional coordinate information is generated by the voltages produced at the touch location.
One of the problems with typical touch mechanisms is that they cannot determine the exact position of the fingers pressed up against a screen if more than one finger is used. One reason that such detection mechanisms have a problem with multi-finger pointing is that a sensing grid is used instead of a large number of point sensors.
FIG. 1 illustrates a sensing grid. This figures shows of series of grids having a predetermined shape. Thus, if two fingers touch the screen at the same time, it cannot be determined whether the grid A′, A, B′, B is caused by the fingers touching A and B, or A′ and B.
There is a problem in what occurs when two fingers touch different vertical lines (points A and B are on different vertical lines and different horizontal lines) so that both two vertical lines and two horizontal lines are activated (i.e. each point having both a different Y and a different Y coordinate). Thus, there is still a need in the art to identify two finger input using a sensing grid.
The presently claimed invention provides a method and apparatus for a touch mechanism to detect a two-finger input on touch screens. Although in the typical sensing grid system, it is difficult to determine the placement of the fingers on the grid, in a first aspect of the invention a square formed by the activation of the lines on the sensing grid caused by two finger touch can be used to make a selection of items that are displayed within this square in order to select, zoom, copy, move, delete, etc., or select a dial to rotate the contents of the grid. In the present invention, a combinatorial matrix touch screen is used to indicate a square with two fingers.
In another aspect of the invention, a 3D virtual touch screen, using the two-finger input of the present invention, permits a Z-coordinate that can be used to rotate the selected item(s) around the Z-axis. In addition, the Z-coordinate can be used to as a “zoom” by changing the size of the selection as a function of the distance to the screen.